In recent years, computer printer technology has evolved to a point where very high resolution images can be transferred to various types of media. Ink jet printing is one particular type of printing that involves the placement of small drops of fluid ink onto a media surface in response to a digital signal. Typically, the fluid ink is placed or jetted onto the surface without physical contact between the printing device and the surface. Within the general area of ink jet printing, the specific method that the ink jet ink is deposited onto the printing surface varies from system to system, and can include continuous ink deposit and drop-on-demand ink deposit.
With regard to continuous printing systems, inks used are typically solvent based such as methyl ethyl ketone and ethanol. Essentially, continuous printing systems function as a stream of ink droplets are ejected and directed by a printer nozzle. The ink droplets are directed additionally with the assistance of an electrostatic charging device in close proximity to the nozzle. If the ink is not used on the desired printing surface, the ink is recycled for later use. With regard to drop-on-demand printing systems, the ink jet inks are typically mixtures of water and water-soluble solvents, e. g., glycols. Essentially, with these systems, ink droplets are propelled from a nozzle by a steam bubble generated by heat (in thermal ink-jet) or by a pressure wave (in piezo ink-jet) such that all of the ink droplets ejected are used to form the printed image.
There are several reasons that ink jet printing has become a popular way of recording images on various media surfaces. Some of these reasons include low printer noise, capability of high speed recording, and multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers. However, though there has been great improvement in ink jet printing, accompanying this improvement are increased demands by consumers in this area, e.g., higher speeds, higher resolution, full color image formation, increased stability, new applications, etc.
The concept of utilizing ink jet technology in the area of ceramics is not a new concept. For example, ceramic “inks” for forming ceramic components in a multi-layer printing process have been disclosed. Specifically, zirconia-containing inks, or ceramic powder-containing inks, have been successfully printed to produce 2.5 mm thick bars. See, Formulation and Multilayer Jet Printing of Ceramic Inks, Song, et al., J. Am. Ceram. Soc. 82 [12] 3374-80 (1990). Additionally, a modified drop-on-demand ink jet printer has been used to build 3-D ceramic structures with cavities and overhangs. Inks used to create these structures consist of zirconia and carbon suspensions. See, Microengineering of Ceramics by Direct Ink-Jet Printing, Mott, et al., J. Am. Ceram. Soc. 82 [7] 1653-8 (1999). In another publication, a continuous ink jet printer was shown to be effective for the direct freeforming of ceramics by multiple overprinting. See, Application of a Continuous Ink Jet Printer to Solid Freeforming of Ceramics, Blazdell, et al., J. Mater. Proc. Tech. 94-102 (1999). A thin, zirconia-alumina, one-dimensional, functionally graded material has been printed by ink jet technology to form a ceramic layer having a step height comparable to the particle diameter dispersed within the composition. Thus, a fine distribution of grains can be formed through ink jet printing technologies. See, Zirconia/alumina Functionally Graded Material Made by Ceramic Ink Jet Printing, Mott, et al., Mater. Sci. Eng. A271 341-352 (1999).
Though ink jet printing technology has been used previously in the ceramic arts, particularly for the building up of ceramic layer(s), it would be useful to provide methods for coloring ceramic and other glazed articles with ink jet ink depositing technologies, including drop-on-demand systems.